This invention relates to hydroforming operations. More particularly the invention relates to coordinated movement of dies used to perform concurrently two or more hydroforming operations in a press.
Hydroforming is a well known metal working process that uses pressurized fluid to expand a closed channel or tubular workpiece outwardly into conformance with the surface of a die cavity. A typical hydroforming apparatus includes a frame having two die sections supported for relative movement between opened and closed positions. The die sections have cooperating recesses, which together define a die cavity having a shape corresponding to a desired final shape for the workpiece. When moved to the open position, the die sections are spaced apart from one another to allow a workpiece to be inserted and removed from the die cavity. When moved to the closed position, the die sections are adjacent one another and enclose the workpiece within the die cavity. Although the die cavity is usually somewhat larger than the workpiece to be hydroformed, movement of the two die sections from the opened position to the closed position may, in some instances, cause some mechanical deformation of the workpiece. In any event, the workpiece is then filled with fluid, typically a relatively incompressible liquid such as water. Fluid pressure within the workpiece is increased to such a magnitude that the workpiece is expanded outward into conformance with the surface contour of the die cavity. As a result, the workpiece is deformed into the desired final shape. Hydroforming is an advantageous process for forming vehicle frame components and other structures because it can quickly deform a workpiece into a desired complex shape.
In a typical hydroforming apparatus, the two die sections are arranged such that a first die section is supported on a displaceable ram, while a second die section is supported on a immovable base. A mechanical or hydraulic actuator is provided for moving the ram and the first die section to the opened position relative to the base and the lower die section, thereby allowing a previously formed workpiece to be removed from the die cavity and a new workpiece to be inserted therein. The actuator also moves the ram and first die section to the closed position relative to the base and second die section before performing the hydroforming process.
Use of a single hydroforming die within a single hydroforming apparatus has been found to be somewhat inefficient from a time consumption standpoint. This is because each operational cycle performed by the hydroforming apparatus involves both a preliminary step of filling the article to be hydroformed with the fluid prior to performing the hydroforming process, and a subsequent step of emptying the hydroforming fluid from the article after performing the hydroforming process. These filling and emptying steps can consume relatively long periods of time, particularly when the articles to be formed are physically large, as is often the case in the manufacture of vehicle frame components. This inefficiency is amplified when the hydroforming apparatus is used to manufacture products in relatively high volumes, as is also the case in the manufacture of vehicle frame components. Thus, it would be desirable to provide an improved structure for a hydroforming apparatus that is capable of performing two or more hydroforming operations concurrently in order to decrease the operation cycle time and to increase overall productivity.
If multiple die cavities are arranged side-to-side in a horizontal configuration in a hydroforming press, the required press tonnage increases in proportion to the number of cavities. By positioning the die cavities in a stacked vertical arrangement in the press, the required press tonnage does not increase. The use of stacked dies allows multiple parts to be made using the same press tonnage as required to form a single part. It is desirable to provide an improved structure for a hydroforming apparatus that is capable of performing two or more hydroforming operations concurrently without increasing press tonnage.
Furthermore, when multiple dies are used to concurrently form parts n a single hydroforming operation, there is need to open the dies, to remove formed workpieces and to insert in the die cavities workpieces to be formed subsequently. Although a ram can assist an operator to open one die cavity, other die cavities not in direct contact with the ram cannot be opened by the ram. This deficiency increases process time and slows the production rate. It is preferable that each die cavity be opened and closed in a process coordinated with movement of the ram.